Principal Investigator/Program Director (Last, first, middle): Hein, Travis, W RESEARCH &RELATED Other Project Information 1. * Are Human Subjects Involved? m Yes l No 1.a. If YES to Human Subjects Is the IRB review Pending? m Yes m No IRB Approval Date: Exemption Number: 1 2 3 4 5 6 Human Subject Assurance Number 2. * Are Vertebrate Animals Used? l Yes m No 2.a. If YES to Vertebrate Animals Is the IACUC review Pending? l Yes m No IACUC Approval Date: Animal Welfare Assurance Number A3895-01 3. * Is proprietary/privileged information m Yes l No included in the application? 4.a.* Does this project have an actual or potential impact on m Yes l No the environment? 4.b. If yes, please explain: 4.c. If this project has an actual or potential impact on the environment, has an exemption been authorized or an environmental assessment (EA) or environmental impact statement (EIS) been performed? m Yes m No 4.d. If yes, please explain: 5.a.* Does this project involve activities outside the U.S. or m Yes l No partnership with International Collaborators? 5.b. If yes, identify countries: 5.c. Optional Explanation: 6. * Project Summary/Abstract 5730-HEINProjSummary.pdf Mime Type: application/pdf 7. * Project Narrative 4585-HEINnarrative.pdf Mime Type: application/pdf 8. Bibliography &References Cited 8012-HEINreferences.pdf Mime Type: application/pdf 9. Facilities &Other Resources 3721-HEINResource-rev.pdf Mime Type: application/pdf 10. Equipment 523-HEINequipment.pdf Mime Type: application/pdf 11. Other Attachments 8699-HEINBioRosa.pdf Mime Type: application/pdf Tracking Number: Other Information Page 5 OMB Number: 4040-0001 Expiration Date: 04/30/2008 Principal Investigator/Program Director (Last, first, middle): Hein, Travis, W Acute periods of retinal ischemia impair subsequent supply of retinal blood flow and have been associated with several ocular diseases leading to visual impairment and blindness. Experimental evidence of diminished retinal blood flow after the initial retinal ischemia suggests that endothelial dysfunction may contribute to persistent retinal damage. Two important endothelium-derived factors involved in regulating retinal blood flow are vasodilator nitric oxide (NO) and vasoconstrictor endothelin-1 (ET-1). Our preliminary studies showed that retinal ischemia via elevated intraocular pressure (IOP) impaired bradykinin-induced NO-mediated dilation and enhanced ET-1-mediated constriction in pig retinal arterioles. Intravitreal administration of superoxide scavenger TEMPOL or endothelin-converting enzyme (ECE) inhibitor phosphoramidon before ischemia preserved vasodilation to bradykinin. Although these pilot studies suggest the involvement of ET-1 and oxidative stress in vascular dysfunction, their interrelationship and the signaling events contributing to the observed impairment remain to be elucidated. Herein, we hypothesize that ischemic insult activates the protein kinase C (PKC)-dependent vascular endothelin system, which leads to superoxide production via NAD(P)H oxidase and a subsequent increase in Rho/Rho kinase activation for the increased vascular tone and a reduced NO-mediated vasodilation. Since our long-term goal is to understand the signaling mechanisms responsible for physiological and pathophysiological regulation of retinal vasomotor function leading to future vascular therapy, the present application will serve the initial step toward this goal by identifying the causal factor and cellular mechanisms contributing to the impairment of vascular function following acute retinal ischemia. We will test the aforementioned hypothesis by pursuing three specific aims: (1) Determine whether enhanced ECE and PKC activities contribute to ischemia-induced dysfunction of retinal arterioles. (2) Determine whether activation of endothelin A/B receptors and vascular p38 mitogen-activated protein kinase/NAD(P)H oxidase signaling contributes to ischemia-induced dysfunction of retinal arterioles. (3) Determine whether enhanced vascular Rho/Rho kinase signaling contributes to ischemia-induced dysfunction of retinal arterioles. We will use both in-vivo and in-vitro approaches with various cellular/molecular techniques to integrate these three aims for elucidating the underlying mechanisms and signaling pathways responsible for the ischemia-induced arteriolar dysfunction in the retina. The results derived from these studies are essential to advance our understanding in the pathogenesis of retinal vascular disease associated with retinal ischemia and may suggest novel targets for future therapeutic interventions. Project Description Page 6